A magnetic recording device such as a computer hard drive has been miniaturized by leaps and bounds in recent years, and the recording density is on the verge of achieving several 10 Gb/in2. Thus, as the reproducing head, a conventional conductive head has reached its limit, and an anisotropic magnetoresistive (AMR) head is now being used.
And, this anisotropic magnetoresistive (AMR) head grew rapidly on a global scale pursuant to the expansion of the personal computer market and so on, and now a high-density giant magnetoresistive (GMR) head is being put into practical use.
In light of the above, manganese alloy of manganese and elements of the platinum group or the like have been used recently as an antiferromagnetic film of a spin valve film used in the GMR head, and expeditious research and development is being conducted for the further improvement of efficiency. Moreover, this antiferromagnetic film is not only used in GMR, but is used in TMR as well, and may also be used in MRAM and the like.
Upon manufacturing the likes of a giant magnetoresistive (GMR) head, for example, the respective layers structuring the head is deposited with the sputtering method.
In general, a target used in sputtering is manufactured with a hot pressing method of sintering powder, a powder metallurgy method such as the HIP method, or a melting method. When manufacturing a manganese alloy target composed from manganese and elements of the platinum group or the like from the foregoing powder metallurgy method, there is an advantage in that the shape yield is favorable and the rupture strength is high.
Nevertheless, in the case of this powder metallurgy method, there are problems in that the specific surface area of the raw material power is large, the amount of oxygen adsorbed is considerably large and, since the amount of oxygen and other impurity elements getting mixed into the manufacturing process of the target increases, the density is low. The existence of oxygen as described above will deteriorate the magnetic property of the film, and this is clearly undesirable.
Formation of the film with the sputtering method is conducted by physically colliding a positive ion such as Ar ion to the target established in the cathode, discharging the materials structuring the target with such collision energy, and laminating films having a composition approximately the same as the target material on the opposing anode side substrate.
Coating with the sputtering method is characterized in that a thin film of an Angstrom level to a thick film of several ten μm can be formed with a stable deposition speed by adjusting the processing time and power supply or the like.
Nevertheless, a particular problem in the case of forming the foregoing film is the density of the sputtering target and the generation of nodules during the sputtering operation.
A manganese alloy target is manufactured by sintering mixed powder in which manganese powder and power of elements of the platinum group or the like are mixed at a prescribed ratio, but since the powders originally have different elemental compositions, variations arise in the particle size of the powder, and there is a problem in that a dense sintered body is difficult to obtain.
In addition, since the film layers are becoming even more miniaturized and dense, the films themselves are also being thinly miniaturized, and, if the formed films are not even, the quality tends to deteriorate. Therefore, it is important to reduce the pores while unifying the elements of the target.
Moreover, when nodules increase on the erosion face of the target, this will induce irregular sputtering, and, in some cases, there may be a problem of a short circuit occurring as a result of abnormal electrical discharge or the formation of a cluster (clumped) film. Simultaneously, enlarged particles begin to float within the sputtering chamber, and a problem arises in that these particles similarly re-adhere on the substrate and cause protrusions on the thin film.
In light of the above, although it was necessary to obtain a high-density sintered target where the elements are even, there is a problem with those obtained with the powder metallurgy method in that the deterioration in density was inevitable, and the generation of nodules and particles could not be avoided.
Meanwhile, with the melting method, adsorption of oxygen and the like arising in powder metallurgy would not occur, and there is a feature in that the density of the target is higher in comparison to a sintered body. Nevertheless, although the Mn alloy target obtained with the melting method has superior characteristics, there is a problem in that it is susceptible to cracking and has a low rupture strength in comparison to a sintered body.
Therefore, a proposal has been made for increasing the rupture strength by using a soluble casting while maintaining the brittleness or making the cast structure a Dendritic structure (Japanese Patent Laid-Open Publication No. 2001-26861). Nevertheless, a cast structure possesses anisotropy, and, even if the rupture strength could be improved by making it a Dendritic structure, it is highly likely that such anisotropy would be reflected in the sputtering deposition and defects would thereby arise in the evenness thereof.
Furthermore, although the sintering method is preferable from the perspective of manufacturing costs and raw material yield, a proposal has also been made for employing a material obtained with the melting method upon performing plastic forming thereto (Japanese Patent Laid-Open Publication No. 2000-160332). Nevertheless, in this case, it is uncertain as to what kind of plastic forming is employed, or the degree of performing such plastic forming, and there are proposals that are merely armchair theories.
As a matter of fact, the foregoing manganese alloy target that is susceptible to cracking and has a low rupture strength is not able to overcome the problems described above unless a specific proposal is provided for resolving the brittleness.